Because identical twins share the same genes and fraternal twins do not, the researchers could identify common genes that result in certain personality traits and predispose people to happiness.

• 由于同卵双生的双胞胎基因完全相同，而异卵双胞胎不完全相同，所以研究人员可以分辨出决定某些性格特征及使人容易快乐的共同基因。